This invention relates to a method for making organic disulfides.
It is known in the art to use a variety of methods to oxidize compounds having the general formula RSH, also known as thiols or mercaptans, to the corresponding disulfide according to the equation: 2R-SH+1/2O.sub.2 .fwdarw.R.sub.2 S.sub.2 +H.sub.2 O. Unfortunately, each known process has its limitations. One method, adapted from the crude oil sweetening process, is thiol oxidation in the presence of copper chloride. The thiol is oxidized in an acidic solution of copper chloride dissolved in a methyl carbitol. This method is relatively expensive and extremely corrosive. Another thiol oxidation process, which is less corrosive, utilizes elemental sulfur. However, since unwanted trisulfides are also produced, only low molecular weight thiols can be oxidized. In yet another thiol oxidation process, which is used for sweetening crude oil, organo-metallo complexes are used to oxidize thiols to disulfides. This process is for primarily low molecular weight thiols and does not result in complete thiol oxidation, as represented by a high final mercaptan sulfur content.
High molecular weight disulfides are used as an additive in the plastics industry as a chain transfer agent in polymerization processes. Furthermore, high purity disulfides are preferred so as not to impart any undesirable color to the end product. Therefore, a non-corrosive process to efficiently produce relatively pure high molecular weight disulfides is desired.